Method of fabricating power semiconductor device and lead frame

Abstract

Disclosed herein are a method of fabricating a power semiconductor device having joiners that (205) vertically extend from outer sides of leads (203, 204) of a tie bar (201) of a power circuit lead frame (20) respectively, while joiners (308) vertically extend from outer sides of leads (303, 307) of a tie bar (301) of a control circuit lead frame (30) respectively to be opposed thereto. Forward end portions (205a) of the joiners (205) are joined to rear surfaces of forward end portions (308a) of the joiners (308) at a device center portion.

What is claimed is: 
     
       1. A method of fabricating a power semiconductor device having a power semiconductor element and a control semiconductor element for controlling said power semiconductor element being stored in the same package, said method comprising the steps of: (a) preparing a power circuit lead frame comprising a power lead group unidirectionally extending from a first tie bar and including a first lead having a power semiconductor element mounting region being loaded with said power semiconductor element, and at least one first joiner being formed on said first tie bar on a side of said power lead group to extend in the same direction as said power lead group;   (b) preparing a control circuit lead frame comprising a control lead group unidirectionally extending from a second tie bar and including a second lead having a control semiconductor element mounting region being loaded with said control semiconductor element, and at least one second joiner being formed on said second tie bar on a side of said control lead group to extend in the same direction as said control lead group;   (c) arranging said power circuit lead frame and said control circuit lead frame to oppose said power lead group and said control lead group to each other and joining forward end portions of said first and second joiners with each other thereby integrating said power circuit lead frame and said control circuit lead frame with each other;   (d) loading said power semiconductor element on said power semiconductor element mounting region and electrically connecting the same with said power lead group;   (e) loading said control semiconductor element on said control semiconductor element mounting region and electrically connecting the same with said control lead group; and   (f) storing said power semiconductor element and said control semiconductor element in the same said package by resin molding,   said steps (d) to (f) being carried out in a state of integrating said power circuit lead frame and said control circuit lead frame with each other through said step (c).   
     
     
       2. The method of fabricating a power semiconductor device in accordance with claim 1, wherein said control circuit lead frame is made of a material satisfying at least either one of conditions of being smaller in thickness than said power circuit lead frame or being easier in working than said power circuit lead frame,   said step (b) includes a step of bending said forward end portion of said second joiner while placing the same on said forward end portion of said first joiner so that rear surfaces of said power semiconductor element mounting region and said control semiconductor element mounting region are flush with each other and   said step (c) includes a step of placing said forward end portion of said second joiner on that of said first joiner and soldering the same to each other.   
     
     
       3. The method of fabricating a power semiconductor device in accordance with claim 1, wherein said control circuit lead frame is made of a material being smaller in thickness than said power circuit lead frame,   said step (a) includes a step of forming a notched step portion having a vertical difference corresponding to the thickness of said control circuit lead frame on an upper surface of said forward end portion of said first joiner,   said step (b) includes a step of bending said forward end portion of said second joiner while placing the same on said forward end portion of said first joiner so that rear surfaces of said power semiconductor element mounting region and said control semiconductor element mounting region are flush with each other, and   said step (c) includes a step of placing said forward end portion of said second joiner on said notched step portion of said first joiner and soldering the same to each other.   
     
     
       4. The method of fabricating a power semiconductor device in accordance with claim 1, wherein said control circuit lead frame is made of a material being smaller in thickness than said power circuit lead frame,   said step (a) includes a step of forming a notched step portion having a vertical difference corresponding to the thickness of said control circuit lead frame on a rear surface of said forward end portion of said first joiner, and   said step (c) includes a step of covering said forward end portion of said second joiner with said notched step portion of said first joiner and soldering the same to each other.   
     
     
       5. The method of fabricating a power semiconductor device in accordance with claim 1, wherein said control circuit lead frame is made of a material satisfying at least either one of conditions of being smaller in thickness than said power circuit lead frame or being easier in working than said power circuit lead frame,   said step (a) includes a step of forming a through hole passing through said forward end portion of said first joiner,   said step (b) includes a step of bending said forward end portion of said second joiner while placing the same on said forward end portion of said first joiner so that rear surfaces of said power semiconductor element mounting region and said control semiconductor element mounting region are flush with each other, and   said step (c) includes a step of placing said forward end portion of said second joiner on that of said first joiner and inserting the same into said through hole by press working.   
     
     
       6. The method of fabricating a power semiconductor device in accordance with claim 1, wherein said control circuit lead frame is made of a material being smaller in thickness than said power circuit lead frame,   said step (a) includes a step of forming a notched step portion having a vertical difference corresponding to the thickness of said control circuit lead frame on an upper surface of said forward end portion of said first joiner, and a step of forming a through hole in said notched step portion,   said step (b) includes a step of bending said forward end portion of said second joiner while placing the same on said notched step portion of said first joiner so that rear surfaces of said power semiconductor element mounting region and said control semiconductor element mounting region are flush with each other, and   said step (c) includes a step of placing said forward end portion of said second joiner on said notched step portion of said first joiner and inserting the same into said through hole by press working.   
     
     
       7. The method of fabricating a power semiconductor device in accordance with claim 1, wherein said control circuit lead frame is made of a material being smaller in thickness than said power circuit lead frame,   said step (a) includes a step of forming a notched step portion having a vertical difference corresponding to the thickness of said control circuit lead frame on a rear surface of said forward end portion of said first joiner, and a step of forming a through hole in said notched step portion, and   said step (c) includes a step of covering said forward end portion of said second joiner with said notched step portion of said first joiner and inserting the same into said through hole by press working.   
     
     
       8. A lead frame being employed for fabricating a power semiconductor device having a power semiconductor element and a control semiconductor element for controlling said power semiconductor element being stored in the same package, said lead frame comprising: a power circuit lead frame comprising a power lead group unidirectionally extending from a first tie bar and including a first lead having a power semiconductor element mounting region being loaded with said power semiconductor element, and at least one first joiner being formed on said first tie bar on a side of said power lead group to extend in the same direction as said power lead group; and   a control circuit lead frame comprising a control lead group unidirectionally extending from a second tie bar and including a second lead having a control semiconductor element mounting region being loaded with said control semiconductor element, and at least one second joiner being formed on said second tie bar on a side of said control lead group to extend in the same direction as said control lead group,   said power circuit lead frame and said control circuit lead frame being so arranged that said power lead group and said control lead group are opposed to each other and rear surfaces of said power semiconductor element mounting region and said control semiconductor element mounting region are flush with each other, forward end portions of said first and second joiners being joined with each other.   
     
     
       9. The lead frame in accordance with claim 8, wherein said control circuit lead frame is made of a material satisfying at least either one of conditions of being smaller in thickness than said power circuit lead frame or being easier in working than said power circuit lead frame, those of said leads of said power lead group and said control lead group having potentials in common being directly joined with each other.   
     
     
       10. The lead frame in accordance with claim 8, wherein said power semiconductor element mounting region and said control semiconductor element mounting region have a first projection and a second projection respectively which project in such directions as to be opposed to each other, and   a forward end portion of said first projection and a forward end portion of said second projection are joined.   
     
     
       11. The lead frame in accordance with claim 8, wherein said power circuit lead frame and said control circuit lead frame are made of low-zirconium oxygen-free copper. 
     
     
       12. The lead frame in accordance with claim 8, wherein the thickness of said power circuit lead frame is not more than ten times as large as that of said control circuit lead frame.